> A) To my low electrical knowledge, heat means not very good efficiency therefore, can I change something or add something to inprove efficiency, consumtion, etc ??
the 1.5 to 3W used in the relay represents only 1 to 0.5% of a slow 300W ride, I wouldn't touch it. these controllers are meant to be cheap, not ultra efficient.
> if you can't make it go forward but can train it to go backwards, simply switch 2 of the 3 power wires and retrain.
I add this: if there are 6 possible training "configurations", then you might need to switch 2 wires; if there are 12 configurations, you shouldn't need to.
regarding your choice of configuration, I can't help you; read posts from people using the regen controller. and I think there's an instructive somewhere. only one hint: make sure the motor rotates in the right direction. with that restriction, there should be only one mode that produces acceptable torque.
(now I see the trace; it seems to go under the big chip, so I'm lost again.)